Devices and system that generate various forms of radiation/ionizing energy are used for various therapeutic/treatment, diagnostic or imaging purposes. For example, various forms of radiation/ionizing energy may be used to inspect an object (such as in airports scanning systems, different security setups, manufacturing and process control) or inspect a patient (such as in a clinic or a hospital, e.g. Cath lab, where a surgeon/therapist operates an X Ray or CT system.)
The medical imaging industry for example is heavily focused on reducing the radiation dose in diagnostic and treatment procedure that include hardware and software modification and operator room procedures. See Miller D L, Balter S, Schueler B A, Wagner L K, Strauss K J, Vano E. “Clinical radiation management for fluoroscopically guided interventional procedures”, Radiology. November 2010; 257(2):321-332. The reporting of radiation dose is one of the QA measurements that are required by Medicare. Furthermore, the Food and Drug Administration in their 2010 “White paper” called for significant reduction of the “unnecessary radiation”. FDA, “White Paper: Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging. In: Administration CfDaRHUSFaD, ed. 2010.
There are two main components that can reduce radiation exposure. The first component is the technical improvements of the x-ray equipment, such as investment in better filtering, collimators, acquisition equipment and image analysis. The other component is the way the operator uses the radiation, which includes the length of exposure, distance from the source to the patient and proper collimation. See Miller D L, Balter S, Schueler B A, Wagner L K, Strauss K J, Vano E. “Clinical radiation management for fluoroscopically guided interventional procedures”, Radiology. November 2010; 257(2):321-332 and Arthur W R, Dhawan J, Norell M S, Hunter A J, Clark A L, “Does cardiologist- or radiographer-operated fluoroscopy and image acquisition influence optimization of patient radiation exposure during routine coronary angiography?”, Br J Radiol. September 2002; 75(897):748-753. The radiation education of the operator/physician is critical to reduce the radiation dose and trained physician utilize significantly lower amounts of radiation. A similar focus to reduce radiation exposure exists in the non-medical areas. For example, the nuclear industry has been very sensitive for several decades to radiation exposure and in many other manufacturing fields there are strict guidelines for minimizing exposure. See Http://www.state.il.us/iema/publications/pdf/IEMA%020032%20Everyday%20Uses-%20of%20Radiation.pdf.
For example, during a fluoroscopy guided, interventional medical procedure, there are periods of time when the operator (usually a physician), even when he/she activates the radiation source which radiates the patient and the staff does not receive the information that is generated by a radiation source. This radiation (and the information in it) are not only wasted but are furthermore needlessly damaging to the patient and the staff/operator of the radiation source. This may be referred to as “Unattended Radiation” (UR) which is undesirable. Thus, in the various different applications in which objects or patients are being inspected, it is desirable to reduce the Unattended Radiation and therefore minimize the exposure to the potentially harmful radiation by the operator and/or patient and it is to this end that the disclosure is directed.
Typical x-ray tubes generate x-ray radiation over a relatively wide solid angle. To avoid unnecessary exposure to both the patient and the medical team, collimators of x-ray absorbing materials such as lead are used to block the redundant radiation. This way only the necessary solid angle of useful radiation exits the x-ray tube to expose only the necessary elements.
Such collimators may assume a variety of designs and x-ray radiation geometry. Collimators can be set up manually or automatically using as input, for example, the dimensions of the cassette holding the plate to limit the radiation to the dimensions of the film in the cassette.
In fluoroscopy the situation is more dynamic than in a single exposure x-ray. The x-ray radiation is active for long periods and the treating physician typically has to stand near the patient, therefore near the x-ray radiation. As a result, it is desired to provide methods to minimize exposure to the medical team. Methods for reducing x-ray radiation intensity have been suggested where the resultant reduced signal to noise ratio (S/N) of the x-ray image is compensated by real-time digital image enhancement. Other methods suggest a collimator limiting the solid angle of the x-ray radiation to a fraction of the image intensifier area and moving the collimator to sweep the entire input area of the image intensifier where the Region of Interest (ROI) is exposed more than the rest of the area. This way, the ROI gets high enough x-ray radiation to generate a good S/N image while the rest of the image is exposed with low x-ray intensity, providing a relatively low S/N image. The ROI size and position can be determined in a plurality of methods. For example, it can be a fixed area in the center of the image or it can be centered automatically about the most active area in the image, this activity is determined by temporal image analysis of a sequence of cine images received from the video camera of the fluoroscopic system. Reference is made now to FIG. 9A which presents a typical layout of a fluoroscopy clinical environment.
X-ray tube 100 generates x-ray radiation 102 directed upward occupying a relatively large solid angle towards collimator 104. Collimator 104 blocks a part of the radiation allowing a smaller solid angle of radiation to continue in the upward direction, go through bed 108 that is typically made of material that is relatively transparent to x-ray radiation and through patient 110 who is lying on bed 108. Part of the radiation is absorbed and scattered by the patient and the remaining radiation arrives at the typically round input area 112 of image intensifier 114. The input area of the image intensifier is typically in the order of 300 mm in diameter but may vary per the model and the technology. The image generated by image intensifier 114 is captured by video camera 116 and then displayed on monitor 118 as image 120.
In modern systems the image intensifier and video camera are often replaced by a rectangle flat panel detector. It would be appreciated that the description below referring to image intensifiers and video cameras is analog for the case of a flat panel detector or other detectors converting x-ray radiation to an electronic image.
Operator 122 is standing by the patient to perform the medical procedure while watching image 120.
The operator has a foot-switch 124. When pressing the switch, continuous x-ray radiation is emitted to provide cine imaging 120. The intensity of x-ray radiation is typically optimized in a tradeoff of low x-ray intensity that is desired to reduce exposure to the patient and the operator and high x-ray intensity that is desired to enable a high quality image 120 (high S/N). With low intensity x-ray radiation and thus low exposure of the image intensifier input area, the S/N of image 120 might be so low that image 120 becomes useless.